In the third stage, day13 AOP implements redis cache, including redis basic usage, persistence, memory optimization, cache breakdown, penetration and avalanche

Half bump 2020-11-09 11:30:06
stage day13 day aop implements

1 AOP Realization Redis cache

1.1 How to understand AOP

name : Section oriented programming
effect : Reduce the coupling of code in the system , And in the condition of not changing the original code, the function of the original method is extended .
The formula : AOP = Pointcut expression + Notification method

1.2 Notification type

1. Pre notice Before the target method is executed
2. The rear notice The target method is executed after execution
3. Abnormal notice When an exception is thrown during the execution of the target method
4. Final notice A notice to be executed at any time
characteristic : The four types of notification mentioned above Cannot interfere with the execution of the target method . It is generally used to record the running state of a program . monitor

5. Surrounding the notification A notification method that is executed before and after the target method is executed This method can control whether the target method runs or not .joinPoint.proceed(); Function as powerful .

1.3 Pointcut expression

understand : Pointcut expression is a judgment of whether a program enters the notification (IF)
effect : When the program is running , When the pointcut expression is satisfied, the notification method is executed , Realize business expansion .
species ( How to write it ):

  1. bean(bean The name of bean Of ID) Can only intercept a specific bean object Only one object can be matched

lg: bean(“itemServiceImpl”)

  1. within( Package name . Class name ) within(“com.jt.service.*”) Can match multiple objects

The principle of coarse-grained matching Match by class

 `3. execution( return type Package name . Class name . Method name ( parameter list )) The most powerful use
lg : execution(* com.jt.service..*.*(..))
The return value type is arbitrary com.jt.service All methods of all classes under the package will be intercepted .
[email protected]( Package name . Annotated name ) Match according to the annotation .`
* 1
* 2
* 3
* 4

1.4 AOP Introductory cases

`package com.jt.aop;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import java.util.Arrays;
@Aspect // I am a AOP Section class
@Component // Give the class to spring Container management
public class CacheAOP {
// The formula = Pointcut expression + Notification method
* About the use of pointcut expressions
* coarse-grained :
* 1.bean(bean Of Id) One class
* 2.within( Package name . Class name ) Multiple classes
* fine-grained
//@Pointcut("within(com.jt.service..*)") // Match multi level directory
@Pointcut("execution(* com.jt.service..*.*(..))") // Method parameter level
public void pointCut(){
// Define pointcut expression Just for space
// difference : pointCut() Represents a reference to a pointcut expression For multiple notifications Shared pointcuts
// @Before("bean(itemCatServiceImpl)") For a single notification . No need to reuse
// Define pre notice , Binding to pointcut expressions . Notice that the binding is the method
* demand : Get information about the target object .
* 1. Get the path of the target method Package name . Class name . Method name
* 2. Gets the type of the target method class
* 3. Get the parameters passed
* 4. Record the current execution time
public void before(JoinPoint joinPoint){
String className = joinPoint.getSignature().getDeclaringTypeName();
String methodName = joinPoint.getSignature().getName();
Class targetClass = joinPoint.getTarget().getClass();
Object[] args = joinPoint.getArgs();
Long runTime = System.currentTimeMillis();
System.out.println(" Method path :" +className+"."+methodName);
System.out.println(" Target object type :" + targetClass);
System.out.println(" Parameters :" + Arrays.toString(args));
System.out.println(" execution time :" + runTime+" millisecond ");
/* @AfterReturning("pointCut()")
public void afterReturn(){
System.out.println(" I'm a post notification ");
public void after(){
System.out.println(" I'm the final notice ");
* The circular notification States
* matters needing attention :
* 1. Parameters must be added to the surround notification ProceedingJoinPoint
* 2.ProceedingJoinPoint Can only be used around notification
* 3.ProceedingJoinPoint If it's a parameter Must be in the first place of the parameter
public Object around(ProceedingJoinPoint joinPoint){
System.out.println(" Surround notification begins !!!");
Object result = null;
try {
result = joinPoint.proceed(); // Execute the next notification or target method
} catch (Throwable throwable) {
System.out.println(" End of surround notification ");
return result;

2 About AOP Realization Redis cache

2.1 Custom cache annotations

problem : How to control Which methods need caching ? cacheFind()
Solution : In the form of custom annotations Define , If Method execution requires caching , Then mark the annotation .
Notes on notes :
1. Annotated name : cacheFind
2. Property parameters :
2.1 key: It should be added manually by the user himself Generally add business name After that, dynamic splicing forms the only key
2.2 seconds: The user can specify the timeout period of the data

`@Target(ElementType.METHOD) // Annotations work for methods
@Retention(RetentionPolicy.RUNTIME) // The operation period is valid
public @interface CacheFind {
public String preKey(); // User ID key The prefix of .
public int seconds() default 0; // If the user does not write, it means that there is no need to time out . If it is written, the user shall prevail .

 Insert picture description here

2.2 edit CacheAOP

`package com.jt.aop;
import com.jt.anno.CacheFind;
import com.jt.config.JedisConfig;
import com.jt.util.ObjectMapperUtil;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import redis.clients.jedis.Jedis;
import java.lang.reflect.Method;
import java.util.Arrays;
@Aspect // I am a AOP Section class
@Component // Give the class to spring Container management
public class CacheAOP {
private Jedis jedis;
* section = The breakthrough point + Notification method
* Annotations associated + Surrounding the notification Control whether the target method is implemented
* difficulty :
* 1. How to get annotation objects
* 2. Dynamic generation key prekey + User parameter array
* 3. How to get the return value type of a method
public Object around(ProceedingJoinPoint joinPoint,CacheFind cacheFind){
Object result = null;
try {
//1. Splicing redis Storing data key
Object[] args = joinPoint.getArgs();
String key = cacheFind.preKey() +"::" + Arrays.toString(args);
//2. Inquire about redis Then judge whether there is data
//redis There's a record in , There is no need to execute the target method
String json = jedis.get(key);
// Get the return value type of the method dynamically Look up Shape down
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
Class returnType = methodSignature.getReturnType();
result = ObjectMapperUtil.toObj(json,returnType);
System.out.println("AOP Inquire about redis cache ");
// Indicates that the data does not exist , Need to query database
result = joinPoint.proceed(); // Implementation target method and notification
// Save the query results to redis In the middle
String json = ObjectMapperUtil.toJSON(result);
// Determine whether the data needs a timeout
}else {
jedis.set(key, json);
System.out.println("aop Execute target method query database ");
} catch (Throwable throwable) {
return result;

3 About Redis Configuration instructions

3.1 About Redis Description of persistence

redis Data persistence is supported by default . When redis When there is data in, the data will be saved to disk regularly . When Redis When the server restarts The specified persistence file will be read according to the configuration file . Realize the recovery of memory data .

3.2 Persistence mode introduction

3.2.1 RDB Pattern

characteristic :
1.RDB The pattern is redis The default persistence policy for .
2.RDB The pattern records Redis Snapshot of memory data . The latest snapshot will cover the previous content all RDB Persistent files take up less space Persistence is more efficient .
3.RDB Patterns are persistent on a regular basis therefore It may lead to the loss of data .

command :

  1. save Requires immediate and immediate persistence Synchronous operation Other redis The operation will get stuck .
  2. bgsave Turn on background operation Asynchronous operations Because of asynchronous operation , So there's no guarantee rdb The files must be up to date and need to wait .

To configure :
1. Persistent file name :
 Insert picture description here
2. Persistent file location
dir ./ The relative path
dir /usr/local/src/redis Absolute path
 Insert picture description here
3.RDB Pattern persistence strategy
 Insert picture description here

3.2.2 AOF Pattern

characteristic :
1.AOF Mode is off by default , It needs to be opened manually by the user
 Insert picture description here

  1. AOF Patterns are asynchronous operations It records the process of user's operation Sure Prevent users from losing data
  2. because AOF Patterns record the running state of a program So the persistence file is relatively large , It takes a long time to recover data . Need to optimize persistence files artificially

To configure :
 Insert picture description here

3.2.2 Summary of persistence operations

1. If data loss is not allowed Use AOF The way
2. If we pursue efficiency Running a small amount of data loss use RDB Pattern
3. If we want to ensure efficiency And to ensure the data You should configure redis The cluster of Host use RDB The slave machine uses AOF

3.3 About Redis Memory strategy

3.3.1 An explanation of the memory policy

explain :Redis Data is stored in memory . If you always want to store data in memory It will inevitably lead to the overflow of memory data .
Solution :

  1. Keep as much as possible in redis Data addition timeout in .
  2. Using algorithms to optimize old data .

3.3.2 LRU Algorithm

characteristic : The best memory optimization algorithm to use .
LRU yes Least Recently Used Abbreviation , namely Recently at least use , Is a common page replacement algorithm , Select the most recent unused page to weed out . The algorithm gives each page an access field , Used to record the time of a page since it was last visited t, When a page has to be eliminated , Select one of the existing pages t The most valuable , That is, the most recently used pages are eliminated .
dimension : Time T

3.3.3 LFU Algorithm

LFU(least frequently used (LFU) page-replacement algorithm). That is, the least frequent use of page replacement algorithm , It is required to replace the page with the lowest reference count at page replacement , Because frequently used pages should have a large number of references . But some pages are used a lot at the beginning , But it will not be used in the future , Such pages will stay in memory for a long time , So we can introduce Use the count register to shift right one bit at a time , The average number of uses to form an exponential decay .
dimension : Times of use

3.3.4 RANDOM Algorithm

Randomly delete data

3.3.5 TTL Algorithm

The algorithm to delete the data with time-out in advance .

3.3.6 Redis Memory data optimization

  1. volatile-lru The data with time-out is used lru Algorithm
    2.allkeys-lru All the data use LRU Algorithm
    3.volatile-lfu The data with time-out is used lfu Algorithm delete
    4.allkeys-lfu All the data are based on lfu Algorithm delete
    5.volatile-random The data of setting time-out time adopts random algorithm
    6.allkeys-random Random algorithms for all data
    7.volatile-ttl Set the timeout data TTL Algorithm
    8.noeviction If memory overflows It will report an error and return . Do nothing . The default value is

 Insert picture description here

4 About Redis Cache interview questions

Problem description : Because of the massive user requests If this time redis Server problem It may cause the whole system to crash .
Running speed :

  1. tomcat The server 150-250 Between JVM tuning 1000/ second
  2. NGINX 3-5 ten thousand / second
  3. REDIS read 11.2 ten thousand / second Write 8.6 ten thousand / second Average 10 ten thousand / second

4.1 Cache penetration

Problem description : Because of users High concurrency Visit in the environment Data that does not exist in the database , Easy to cause cache penetration .
How to solve : Set up IP Current limiting operation nginx in Or Microsoft Service Mechanism API Gateway implementation .

4.2 Cache breakdown

Problem description : Because of users High concurrency In the environment , Because some data existed in memory before , But for special reasons ( Data timeout / Data accidentally deleted ) Lead to redis Cache invalidation . So that a large number of users' requests directly access the database .
Common saying : Take advantage of his illness To kill him
How to solve :
1. When setting the timeout Don't set the same time .
2. Set multi level cache
 Insert picture description here

4.3 Cache avalanche

explain : because High concurrency Under the condition of Yes A lot of data failed . Lead to redis The hit rate is too low . It allows users to access the database directly ( The server ) Leading to a rout , It's called cache avalanche .
Solution :
1. Don't set the same timeout random number
2. Set multi level cache .
3. Improve redis Cache hit rate adjustment redis Memory optimization strategy use LRU And so on .
 Insert picture description here

本文为[Half bump]所创,转载请带上原文链接,感谢

  1. 【计算机网络 12(1),尚学堂马士兵Java视频教程
  2. 【程序猿历程,史上最全的Java面试题集锦在这里
  3. 【程序猿历程(1),Javaweb视频教程百度云
  4. Notes on MySQL 45 lectures (1-7)
  5. [computer network 12 (1), Shang Xuetang Ma soldier java video tutorial
  6. The most complete collection of Java interview questions in history is here
  7. [process of program ape (1), JavaWeb video tutorial, baidu cloud
  8. Notes on MySQL 45 lectures (1-7)
  9. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  10. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  11. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  12. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  13. 【递归,Java传智播客笔记
  14. [recursion, Java intelligence podcast notes
  15. [adhere to painting for 386 days] the beginning of spring of 24 solar terms
  16. K8S系列第八篇(Service、EndPoints以及高可用kubeadm部署)
  17. K8s Series Part 8 (service, endpoints and high availability kubeadm deployment)
  18. 【重识 HTML (3),350道Java面试真题分享
  19. 【重识 HTML (2),Java并发编程必会的多线程你竟然还不会
  20. 【重识 HTML (1),二本Java小菜鸟4面字节跳动被秒成渣渣
  21. [re recognize HTML (3) and share 350 real Java interview questions
  22. [re recognize HTML (2). Multithreading is a must for Java Concurrent Programming. How dare you not
  23. [re recognize HTML (1), two Java rookies' 4-sided bytes beat and become slag in seconds
  24. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  25. RPC 1: how to develop RPC framework from scratch
  26. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  27. RPC 1: how to develop RPC framework from scratch
  28. 一次性捋清楚吧,对乱糟糟的,Spring事务扩展机制
  29. 一文彻底弄懂如何选择抽象类还是接口,连续四年百度Java岗必问面试题
  30. Redis常用命令
  31. 一双拖鞋引发的血案,狂神说Java系列笔记
  32. 一、mysql基础安装
  33. 一位程序员的独白:尽管我一生坎坷,Java框架面试基础
  34. Clear it all at once. For the messy, spring transaction extension mechanism
  35. A thorough understanding of how to choose abstract classes or interfaces, baidu Java post must ask interview questions for four consecutive years
  36. Redis common commands
  37. A pair of slippers triggered the murder, crazy God said java series notes
  38. 1、 MySQL basic installation
  39. Monologue of a programmer: despite my ups and downs in my life, Java framework is the foundation of interview
  40. 【大厂面试】三面三问Spring循环依赖,请一定要把这篇看完(建议收藏)
  41. 一线互联网企业中,springboot入门项目
  42. 一篇文带你入门SSM框架Spring开发,帮你快速拿Offer
  43. 【面试资料】Java全集、微服务、大数据、数据结构与算法、机器学习知识最全总结,283页pdf
  44. 【leetcode刷题】24.数组中重复的数字——Java版
  45. 【leetcode刷题】23.对称二叉树——Java版
  46. 【leetcode刷题】22.二叉树的中序遍历——Java版
  47. 【leetcode刷题】21.三数之和——Java版
  48. 【leetcode刷题】20.最长回文子串——Java版
  49. 【leetcode刷题】19.回文链表——Java版
  50. 【leetcode刷题】18.反转链表——Java版
  51. 【leetcode刷题】17.相交链表——Java&python版
  52. 【leetcode刷题】16.环形链表——Java版
  53. 【leetcode刷题】15.汉明距离——Java版
  54. 【leetcode刷题】14.找到所有数组中消失的数字——Java版
  55. 【leetcode刷题】13.比特位计数——Java版
  56. oracle控制用户权限命令
  57. 三年Java开发,继阿里,鲁班二期Java架构师
  58. Oracle必须要启动的服务
  59. 万字长文!深入剖析HashMap,Java基础笔试题大全带答案
  60. 一问Kafka就心慌?我却凭着这份,图灵学院vip课程百度云